<!DOCTYPE html>
<html lang="en" >
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<div id="app"> 下拉框： <select v-model="selected"> <option disabled value="">请选择</option> <option>A</option> <option>B</option> <option>C</option>
</select> <span>选中的值: {{ selected }}</span>
</div>
<script src="vue.js"></script>

<script>
    var vm = new Vue({
        el: '#app', data: {
            selected: ''
        }
    });
</script>
</body>

</html>